Reducing nitrogen oxide emissions in boilers at moistening of blowing air in heat recovery systems

Abstract

Considered indicators of reducing harmful emissions into the environment by gas-fired water-heating and steam boilers of the municipal heat-power engineering, which are equipped with heat-recovery systems of boiler exhaust-gases. The results of studies on the relative decrease of emissions of nitrogen oxides and other harmful substances generated during fuel combustion in boilers when used for boilers complex heat-recovery plants for heating heat-network water and water for a chemical water-purification system of a boiler plant, as well as for heating and humidifying combustion air are presented. It is shown that the use of such complex heat-recovery systems, due to the useful heat of exhaust-gases from boilers, provides a reduction in fuel consumption and, consequently, the volumes of harmful emissions generated during its combustion, by 8–12%, depending on the mode of operation of boilers during the heating period. The efficiency of using combustion-air humidifying in these installations to decrease the level of formation of nitrogen oxides in the combustion area of boilers is considered. It is also shown that the use of these systems provides a decrease emissions of nitrogen oxides to the environment by up to 60% by reducing the combustion temperature in the combustion area at moisture introduction with the combustion air and, as a result, suppression of formation these oxides during fuel combustion in boilers. The substantiation of the accuracy of the obtained calculated values of the levels of relative decrease of emissions of nitrogen oxides with the moisture introduction into the boiler by comparing them with experimental data is given. Comparative of the results shows a good agreement between the calculated and experimental data.